1. Technical Field
The present invention relates to a light modulation element positioning method for a projector, and a projector.
2. Related Art
Currently, such a projection method is known which positions two projectors such that pixels of a light modulation element included in one of the two projectors agree with corresponding pixels of a light modulation element included in the other projector. By this method, identical images can be projected from the projectors onto the same screen (this method is called “stack projection”). Image light projected by the stack projection has approximately twice higher luminance, and becomes considerably bright image light when projected on the screen. Also, such a projection method has been practiced which shifts the pixels of the light modulation element of the one projector from the corresponding pixels of the light modulation element of the other projector by ½ pixel for each in an oblique direction and projects identical images from the respective projectors to increase resolution of the images (this method is called “pixel shift projection”)
In case of the stack projection or the pixel shift projection described above, however, the positions of the two projectors need to be controlled with high accuracy, and generally only a skilled person can perform appropriate positioning. Particularly in case of the pixel shift projection, a reference and a target for positioning are difficult to be determined in setting a desired pixel shift condition. Thus, the control required for the pixel shift projection becomes more difficult.
Also, a projector which includes two light modulation element units (first light modulation element unit and second light modulation element unit) is known (see JP-A-10-304284, for example). According to the projector disclosed in JP-A-10-304284, the first light modulation element unit receives first polarized light component (P-polarized light component) light from a light source and supplies first image light, and the second light modulation element unit receives second polarized light component (S-polarized light component) light from the light source and supplies second image light. The first image light and the second image light are combined by a polarized light combining system and projected on a screen through a projection system. Bach of the first light modulation element unit and the second light modulation element unit has light modulation elements for R, G, and B lights and a combining system for combining the R, G, and B lights outputted from the light modulation elements for R, G, and B lights as one unit.
According to the projector shown in JP-A-10-304284 which includes the two light modulation element units (the first light modulation element unit and the second light modulation element unit), the respective light modulation elements for R, G, and B lights (liquid crystal panels) of the first light modulation element unit are highly accurately positioned such that the corresponding pixels of the respective light modulation elements agree with one another, and also the respective light modulation elements for R, G, and B lights (liquid crystal panels) of the second light modulation element unit are highly accurately positioned such that the corresponding pixels of the respective light modulation elements agree with one another. Then, the first light modulation element unit and the second light modulation element unit are highly accurately positioned. By this method, it is expected that the first image light outputted from the first light modulation element unit and the second image light outputted from the second light modulation element can be displayed in the desired pixel shift condition.
However, when the first image light outputted from the first light modulation element unit and the second image light outputted from the second light modulation element unit are desired to be displayed on the screen in the pixel shift condition for shifting ½ pixel for each pixel in an oblique direction according to the projector disclosed in JP-A-10-304284, the positions of the first light modulation element unit and the second light modulation element unit need to be highly accurately controlled at the time of assembly of the projector. As explained above, in case of the pixel shift projection, a reference and a target for positioning are difficult to be determined in setting the desired pixel shift condition. Thus, the positioning becomes further difficult, and the productivity of the projector lowers.